General guidelines for number of samples & location of samples?

• A. 2 windowsills, 2 window troughs, and 2 floor samples in 6 room equivalents.
• B. Only one sample per room.
• C. 1 windowsill, 1 window trough, and 1 floor sample in up to 4 room equivalents + 1 floor sample adjacent to the work area.
• D. Three samples total with no specified locations.

Answer: (C)

When planning clearance sampling after lead work, you want a plan that captures dust from surfaces most likely to carry residues and spreads the samples across the spaces affected. The best approach uses three specific surface types—windowsills, window troughs, and floors—and applies them across the rooms impacted, with an extra floor sample right next to the work area. This combination targets where lead dust tends to settle (windowsills and troughs collect settled dust from activities and airflow; floors reflect overall room contamination) and provides coverage across multiple room equivalents to represent the whole area, while also checking the area closest to disturbance.

This approach is preferable because it balances representativeness with practicality: sampling only a single surface per room would miss variability in dust deposition; taking too few samples or not specifying surface types could overlook contamination on surfaces that commonly harbor dust. By including all three surface types and distributing samples across several room equivalents plus a near-work-area floor sample, you get a reliable picture of the overall cleanliness and localized hotspots.